The use is known of so-called “tyre-changing” machines which permit fitting and removing the tyre to/from the relative rim of a vehicle wheel. Such tyre-changing machines are used, e.g., in garages to perform maintenance or replacement jobs on the rim and/or the tyre itself
Generally, known tyre-changing machines comprise a frame for supporting means for gripping and rotating the rim of a wheel, and for supporting a tool carrier arm having at least a tool suitable for removing and/or fitting the tyre from/to the rim.
The supporting frame generally comprises a base for supporting the rim gripping and rotating means, commonly made up of a specific self-centring spindle positioned at a preset height off the ground.
The supporting frame also comprises a vertical upright which extends from the rear portion of the base and which supports a specific tool carrier arm which is adjustable along a horizontal direction depending on the specific dimensions of the wheel to be worked.
The tool carrier arm has a vertically adjustable removal/fitting tool.
The use is also known of at least an auxiliary arm having a specific bead-pressing tool usable to make the rim fitting/removal operations easier, in particular for low profile and “runflat” tyres.
For example, a first type of auxiliary arm comprises a horizontal arm hinged to the vertical upright of the supporting frame and which can be turned like a weathervane, with which the bead-pressing tool is associated vertically movable.
A second type of auxiliary arm comprises an articulated arm, hinged to the vertical upright of the supporting frame and suitable for supporting the bead-pressing tool movably and vertically.
A further possible solution also envisages the use of a supplementary supporting upright, generally fastened to the supporting frame alongside the main upright, suitable for supporting the auxiliary arm and the relative bead-pressing tool.
During the removal phase, an operator positions and locks the rim of the wheel to be worked on the spindle and, by means of a specific bead-breaking tool, performs a preliminary operation involving the detachment of the tyre bead from the annular flanges of the rim.
Subsequently, the operator adjusts the position of the removal/fitting tool according to the specific dimensions of the wheel, positioning it in correspondence to a section of the tyre to be raised above the edge of the rim, and moves the tool so as to extract a portion of the bead above the rim.
The auxiliary arm is turned until the bead-pressing tool is positioned in correspondence to a portion of the tyre substantially opposite the tyre raised portion by means of the removal/fitting tool.
In particular, the pressure applied by means of the bead-pressing tool favours the extraction of the tyre bead.
Subsequently, the wheel is partially rotated to allow the bead to be extracted and, during such rotation, the bead-pressing tool continues to apply a pressure on the tyre, following the rotation of the wheel.
When the bead-pressing tool is in the proximity of the removal/fitting tool, then the operator lifts the bead-pressing tool by operating the specific control lever and positions the auxiliary arm in an idle position so as not to hinder the movements of the operator during the removal of the tyre from the rim.
The complete rotation of the wheel then permits completing the extraction of the wheel bead above the edge of the rim.
In the same way, during fitting, an operator positions and locks the rim of the wheel to be worked on the spindle and suitably positions the tyre to be fitted on the rim.
Subsequently, the operator adjusts the position of the removal/fitting tool according to the specific dimensions of the wheel, positioning it in correspondence to a section of the tyre and pressing it below the edge of the rim.
The auxiliary arm is rotated until the bead-pressing tool is positioned in correspondence to a portion of the tyre, in the proximity of the removal/fitting tool.
In particular, the pressure applied by the bead-pressing tool favours the insertion of the tyre bead.
Subsequently, the wheel is partially rotated to allow inserting the bead and, during such rotation, the bead-pressing tool continues to apply a pressure on the tyre, following the rotation of the wheel.
When the bead-pressing tool is in the proximity of the removal/fitting tool, then the operator lifts the bead-pressing tool by operating the specific control lever and positions the auxiliary arm in an idle position so as not to hinder the movements of the operator during the removal of the tyre from the rim.
The complete rotation of the wheel then permits completing the insertion of the wheel bead below the edge of the rim.
The known solutions described above do however have a number of drawbacks.
In particular, the presence of the auxiliary arm, especially if supported by a specific supplementary upright, considerably increases the overall dimensions of the tyre-changing machine.
In particular, once drawn up in an idle position, with the bead-pressing tool moved away from the rim gripping and rotating means, the supplementary arm has greater overall dimensions in correspondence to the rear portion of the tyre-changing machine.
Furthermore, after being used for tyre removal/fitting operations, the auxiliary arm must necessarily be repositioned in idle position, with the bead-pressing tool spaced apart from the rim gripping and rotating means, so as not to hinder the movements of the operator during the removal or positioning of the tyre from/on the rim.
Consequently, such operation inevitably involves an increase in the time needed to complete the tyre removal/fitting operations.